Molding is a process by virtue of which a molded article can be formed from molding material by using a molding system. Various molded articles can be formed by using the molding process, such as an injection molding process. One example of a molded article that can be formed, for example, from polyethylene terephthalate (PET) material is a preform that is capable of being subsequently blown into a beverage container, such as, a bottle and the like.
A typical molding system includes inter alia an injection unit, a clamp assembly and a mold assembly. The injection unit can be of a reciprocating screw type or of a two-stage type. The clamp assembly includes inter alia a frame, a movable platen, a fixed platen and an actuator for moving the movable platen and to apply tonnage to the mold assembly arranged between the fixed and movable platens. The mold assembly includes inter alia a cold half and a hot half. The hot half is usually associated with one or more cavities (and, hence, also sometimes referred to by those of skill in the art as a “cavity half”), while the cold half is usually associated with one or more cores (and, hence, also sometimes referred to by those of skill in the art as a “core half”). The one or more cavities together with one or more cores define, in use, one or more molding cavities. The hot half can also be associated with a melt distribution system (also referred to sometimes by those of skill in the art as a “hot runner”) for melt distribution. The mold assembly can be associated with a number of additional components, such as neck rings, neck ring slides, ejector structures, wear pads, etc.
As an illustration, injection molding of PET material involves heating the PET material (ex. PET pellets, PEN powder, PLA, etc.) to a homogeneous molten state and injecting, under pressure, the so-melted PET material into the one or more molding cavities defined, at least in part, by the aforementioned one or more cavities and one or more cores mounted respectively on a cavity plate and a core plate of the mold assembly. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient enough to keep the cavity and the core plates together against the pressure of the injected PET material. The molding cavity has a shape that substantially corresponds to a final cold-state shape of the molded article to be molded. The so-injected PET material is then cooled to a temperature sufficient to enable ejection of the so-formed molded article from the mold. When cooled, the molded article shrinks inside of the molding cavity and, as such, when the cavity and core plates are urged apart, the molded article tends to remain associated with the core. Accordingly, by urging the core plate away from the cavity plate, the molded article can be demolded, i.e. ejected from the core piece. Ejection structures are known to assist in removing the molded articles from the core halves. Examples of the ejection structures include stripper plates, ejector pins, etc.
One consideration for economical operation of the molding system is cycle time or, in other words, time that elapses between a point in time when the cavity and core halves are closed and the molded articles are formed and a subsequent point in time when they are opened and the molded articles are removed. As one will appreciate, the shorter the cycle time, the higher the number of molded articles that can be produced in a particular mold of a given size in a given time interval. One attempt to minimize the cycle time is a so-called “post-mold treatment” process. Generally speaking, the post-mold treatment process involves removing the molded articles from the mold once they are sufficiently cooled to enable ejection of the molded articles without causing significant deformation to the molded articles during its transfer to an auxiliary cooling structure. Post-mold treatment then occurs independently (but in parallel) to the injection cycle of the molding machine.
An example of the auxiliary cooling structure is disclosed in a commonly owned U.S. Pat. No. 7,104,780 issued to Domodossola et al. on Sep. 12, 2006. More specifically, Domodossola et al. discloses a platen-mounted, post-mold cooling apparatus for handling molded parts in an injection molding machine having a fixed platen, a movable platen, a core half, and a cavity half. A take-off device coupled to the fixed platen is configured to remove molded parts from either the core half or the cavity half. A treatment device coupled to the movable platen is configured to cool the molded parts carried by the take-off device. The take-off device extracts the just molded parts from the mold's core half and then moves linearly outboard of the mold halves. The subsequent movement of the movable platen to close the mold in the next molding cycle causes the treatment device's pins to engage the molded parts in the take-off device part carriers. When the movable platen opens again, the molded parts are extracted from the part carriers by the treatment device pins. When the movable platen is fully open, the treatment device is rotated to eject the cooled parts from the machine.